Evaluate resonance structures and make sure all equally-contributing resonance structures have been represented. Assign formal charge to every atom in the structure. Write the skeleton structure. Count up the total number of valence electrons. Subtract 2 electrons for every bond in the skeleton structure. Determine how many additional electrons each atom needs to be satisfied. If NEED = HAVE, add lone pairs. If NEED > HAVE, add one extra bond for each two electrons that NEED and HAVE differ. If HAVE > NEED and the central atom's atomic number is ≥ 15, add lone pairs to satisfy and extra electrons go on central atom. What is the process to evaluate resonance structures and assign formal charge to atoms?